Valve seat unit for an injector for injecting fuel, and an injector having such a valve seat unit

Abstract

The present invention relates to a valve seat unit for an injector for injecting fuel, preferably for injecting a gaseous fuel, in particular hydrogen, comprising: at least one passage running through the valve seat unit for conducting fuel, wherein an opening contour of the at least one passage is designed to interact with an armature element in order to close or open the passage for a fuel flow by lowering or lifting the armature element onto / from the valve unit, characterized in that the valve seat unit comprises at least a first component and a second component which are arranged one above the other, in particular in layers one above the other, wherein the first component and the second component are thermally separated from one another in such a way that a thermal conductivity from the first component to the second component is not more than 0.3 W / (m·K), preferably not more than 0.1 W / (m·K) and more preferably not more than 0.05 W / (m·K).

Description

[0001] Valve seat unit for an injector for injecting fuel, and an injector with such a valve seat unit.

[0002] The present invention relates to a valve seat unit for an injector for injecting fuel and to an injector with such a valve seat unit.

[0003] With increasingly stringent emissions limits worldwide and ambitious climate protection goals, the environmental requirements for internal combustion engines are constantly rising. The aim in the foreseeable future is low-emission or even emission-free drive technologies that meet even the strictest emissions limits and make a significant contribution to achieving climate protection goals. For combustion-based technologies, these goals are only achievable with the use of climate-neutral, regeneratively produced fuels that cause no emissions whatsoever along the entire value chain (so-called "zero-emission" fuels).

[0004] With current conventional gasoline, diesel and gas engines, the requirements for emission-free combustion are not achievable – even with the use of so-called e-fuels, e.g. a synthetically produced OM E-fuel, for the production of which only renewable energy is required – because the emission of harmful exhaust gases such as nitrogen oxides (NOx), unburned hydrocarbons (UHC) and soot cannot be completely reduced with current technologies.

[0005] Hydrogen combustion engines, which represent a promising alternative drive system, have therefore moved into focus. However, these currently exist almost exclusively in very small numbers or as demonstrators with a low level of development. Hydrogen produced using renewable energy would meet all the requirements of "zero emission" technology, as it can be combusted without producing emissions.

[0006] In passenger cars, for example, hydrogen engines with port fuel injection (PFI) are used, in which the fuel is thoroughly mixed with air for a sufficient amount of time before entering the combustion chamber. Hydrogen engines with direct injection of the fuel into the combustion chamber (direct injection, DI) play practically no role today, but compared to the PFI concept, they offer, among other things, higher efficiency, more stable combustion, and the elimination of the risk of backfire into the intake manifold.

[0007] In direct-injection hydrogen engines, a distinction is typically made regarding the maximum injection pressure in the injector (< 60 bar: low pressure, > 60 bar: high pressure), although the boundaries are not clearly defined and the transitions are gradual. Higher pressures offer the potential for a shorter injection duration in a later phase of compression at higher combustion chamber pressures, resulting in increased efficiency and improved combustion stability. However, overall efficiency decreases if prior compression of the hydrogen is necessary.

[0008] If the hydrogen is produced entirely from renewable energy sources, hydrogen combustion engines can achieve virtually climate-neutral operation. Furthermore, numerous other advantages are offered: • Use of established, highly mature technologies and existing production facilities

[0009] • Unlimited availability of hydrogen through electrolysis of water

[0010] • Use of the existing filling station system possible (after appropriate conversion) with fast refueling times

[0011] • (Almost) emission-free conversion of hydrogen during combustion is possible, as it is CO2-neutral, with only minimal CO, UHC, particle and soot emissions (caused solely by lubricants in the supply system, below the measurement limit) and only minimal NOx emissions through a suitable combustion process (possibly with exhaust gas recirculation, SCR catalyst)

[0012] • significantly lower hydrogen purity requirements compared to fuel cell drives

[0013] • No need for platinum in manufacturing, as with fuel cells

[0014] However, in addition to these numerous advantages over other drive concepts, there are also some challenges that need to be overcome in the development of hydrogen combustion engines:

[0015] • Low molecular weight of hydrogen, resulting in a low density and consequently a low volumetric energy density (but high mass-specific energy density); see Table 1

[0016] • Provision of a correspondingly high volume flow rate during the injection of hydrogen

[0017] • corresponding provision of large flow cross-sections in the injector and thus significantly larger actuator strokes required than with conventional drive systems

[0018] • Mixture preparation in the combustion chamber / Influence of the injection jet / Ignition behavior with minimal injection

[0019] • High local temperatures in the combustion chamber can lead to increased thermal NOx formation, which necessitates the development of a suitable combustion process (for example, charge stratification to avoid stoichiometric

[0020] Combustion, exhaust gas recirculation, exhaust gas aftertreatment)

[0021] Table 1: Mass- and volume-specific calorific value of diesel and hydrogen

[0022] The objective of the present invention is to overcome or mitigate the challenges and disadvantages partially listed above and to provide a correspondingly enhanced valve seat unit for an injector for injecting gas such as hydrogen, or to propose an injector equipped therewith.

[0023] In particular, the valve seat assembly is designed to better withstand the very high temperatures typically found in the combustion chamber, preventing, for example, melting or excessive heating of a sealing element of the anchor element at the opening contour of the valve seat assembly. This can lead to leaks in the system and thus to the uncontrolled escape of fuel.

[0024] The aforementioned objective is achieved by implementing the present invention, which has all the features of claim 1.

[0025] A valve seat unit according to the invention for an injector for injecting fuel, preferably for injecting a gaseous fuel, in particular hydrogen, comprises at least one through-line running through the valve seat unit for conveying fuel, wherein an opening contour of the at least one through-line is designed to interact with an anchor element in order to close or release the through-line (5) for a fuel flow by placing or lifting the anchor element from the valve unit.The valve seat unit according to the invention is characterized in that the valve seat unit comprises at least a first component and a second component which are arranged one above the other, in particular in a layered arrangement, wherein the first component and the second component are thermally separated from each other in such a way that a thermal conductivity from the first component to the second component is no more than 0.2 W / (m K), preferably no more than 0.1 W / (m K) and preferably no more than 0.05 W / (m K).

[0026] By incorporating multiple components into the valve seat assembly, the thermal conductivity of the valve seat assembly is reduced, thus lowering the temperature of the valve seat assembly on the side facing the armature element. Previously, it was problematic that the very high temperatures in the combustion chamber led to heating of the injector and the valve seat assembly itself, potentially causing melting or a significant temperature increase in parts of the armature element, particularly the sealing element that closes the opening of a passage through the valve seat assembly. In the worst-case scenario, this could lead to leaks in the system and consequently to the uncontrolled escape of fuel.The increase in the temperature of the valve seat unit is particularly problematic when using gaseous fuels, especially hydrogen, since, unlike liquid fuels, these only cool the injector minimally when flowing through it.

[0027] The invention therefore proposes to construct the valve seat assembly in multiple layers, such that low thermal conductivity exists at the transition between a first and a second component of the valve seat assembly. This ensures that the elevated temperature does not reach the anchor element interacting with the valve seat assembly and thus prevent damage to a sealing element provided on the anchor element. When such a valve seat assembly is used in an injector, the first component, which faces a combustion chamber, is referred to as the hot valve part, and the second component, which faces away from the combustion chamber, is referred to as the cold valve part, since there are significant temperature differences between the different components.

[0028] In particular, it is provided that the thermal conductivity from the first component, which faces a combustion chamber, to the second component, which faces an anchor element of an injector, is not greater than 0.30 W / (m K) or 0.10 W / (m K), and in particular not greater than 0.05 W / (m K).

[0029] According to an optional further development of the present invention, it can be provided that the first component and the second component are arranged apart from each other.

[0030] To achieve the low thermal conductivity between the first component and the second component, the components of the valve seat unit can be spaced apart from each other and do not contact each other directly.

[0031] To achieve a defined alignment of the two components of the valve seat assembly, a welded connection can preferably be provided, through which the two components are connected. In particular, the welded connection can be either spot welds or continuous welds and / or represent the only direct connection between the first and second components.

[0032] When creating the weld, care must be taken to ensure that the weld is quite thin so that the thermal conductivity between the first and second components does not exceed the limit specified above. The weld therefore bridges the gap between the first and second components at only a few points and / or in small areas, allowing the gap between the first and second components to continue acting as a thermal insulator.

[0033] According to a further advantageous embodiment of the present invention, an insulating component can be arranged between the first component and the second component, which prevents direct contact between the first component and the second component and / or reduces a dead space formed by the spacing of the first component from the second component, wherein the insulating component preferably has a low thermal conductivity not exceeding 0.3 W / (m K), preferably 0.1 W / (m K), and / or is made of a ceramic material.

[0034] Dividing the valve seat assembly into several components that are spaced apart and do not directly touch each other creates a dead space that must be filled with fuel when the valve seat assembly is used in an injector. To reduce the amount of fuel required in the valve seat assembly, an insulating component can be arranged in the dead space, for example, by contacting the two components.

[0035] It is clear to the expert that this insulation component can also be provided instead of a welded connection between the two components, resulting in a layered structure in which the insulation component forms the middle layer and the first component and the second component are arranged on one side of the insulation component, respectively.

[0036] According to a further embodiment of the present invention, the first component and the second component of the valve seat assembly may not be in direct contact with each other, preferably being connected to each other via an insulating component and / or a welded connection. Furthermore, according to a further optional modification of the present invention, the first component may comprise an outlet contour of the at least one through-line, and the second component may comprise the opening contour of the at least one through-line.

[0037] The valve seat assembly primarily serves to conduct fuel, but this flow can be interrupted by placing an anchor element, which closes the opening contour of the valve seat assembly. To receive the fuel, the valve seat assembly has an opening contour that is fluidically connected to the flow line and terminates in an outlet contour at the opposite end of the assembly. The flow line thus connects the opening contour on one side of the valve seat assembly with the outlet contour on the other side. The minimum cross-sectional area of ​​the flow line determines the maximum amount of fuel that can flow through the valve seat assembly. It is clear to those skilled in the art that there can be multiple bores for the flow line within the valve seat assembly.

[0038] According to a further optional embodiment of the present invention, the first component may have a thermal conductivity greater than the thermal conductivity between the first component and the second component (or the insulation component), preferably wherein the thermal conductivity of the first component is at least 1 W / (m K), preferably at least 10 W / (m K). Furthermore, it may also be provided that the second component has a thermal conductivity of at least 1 W / (m K), preferably at least 10 W / (m K).

[0039] Typically, the first component and / or the second component is made of stainless steel or titanium, which have a thermal conductivity in the range of 15 to 22 W / (m K). According to a further advantageous modification of the present invention, the second component can have a first flat surface in which the opening contour of the through-line is arranged, wherein the opening contour is a circumferential groove formed in the first flat surface, preferably wherein at least one conduit section, in particular in the form of a bore or a slot, extends from a groove base of the circumferential groove to a transfer contour of the through-line for directing fuel to the first component of the valve unit.

[0040] By providing a continuous groove on the first flat side of the second component (which faces the anchor element when installing the valve seat unit in an injector), at the base of which at least one pipe section extending towards the outlet contour is arranged, the contact area to a sealing element of an anchor element attached to the first flat side is reduced, resulting in less heat transfer to a sealing element of the anchor element.

[0041] Alternatively and / or additionally, according to the present invention, it can be provided that the second component has a second flat side facing the first component and in which a transfer contour of the through-line for conveying fuel to the first component is arranged, wherein the transfer contour is a circumferential groove formed in the second flat side, preferably wherein at least one line section, in particular in the form of a bore or a slot, is formed from a groove base of the circumferential groove towards the opening contour of the valve unit.

[0042] Providing a circumferential groove on the second flat side (which faces the first component) of the second component is also advantageous with regard to the assembly of the valve seat unit, since regardless of the rotational position of the second component, the transfer contour is always in the same place.

[0043] According to an advantageous modification of the present invention, the first component may have a plate-like basic structure with a first flat side and a second flat side, wherein the first flat side faces the second component and the second flat side faces away from the second component and has an outlet contour of the valve unit.

[0044] Preferably, it can be provided that a through-line section connecting the first flat side and the second flat side of the first component defines a minimum line cross-section along the through-line of the valve unit.

[0045] This is particularly advantageous for delivering a uniform fuel flow through the valve seat unit, since the crucial minimum cross-sectional area of ​​the line is then located in the first component, which has a particularly low complexity and can be modified without much effort.

[0046] Furthermore, according to the present invention, it can be provided that the first component and / or the second component is / are rotationally symmetrical.

[0047] The invention further relates to an injector for injecting fuel, preferably for injecting a gaseous fuel, in particular hydrogen, which has a valve seat unit according to one of the aspects defined above.

[0048] It can advantageously be provided that such an injector further comprises an injector housing for receiving and arranging injector components, an anchor element which is movably arranged in the injector housing along an axial direction of the injector, and a valve seat unit according to one of the preceding claims, wherein the anchor element is designed to close or release the through-line of the valve seat unit by means of an axial movement in order to enable or prevent fuel flow through the through-line.

[0049] Furthermore, it may be provided that the valve seat unit is fixedly arranged in the injector housing and, unlike the anchor element, is not movable in the axial direction of the injector.

[0050] A further advantage is that the valve seat unit is circumferentially enclosed by the injector housing, in particular directly circumferentially enclosed by the injector housing, so that the first component of the valve seat unit can establish good thermal conductivity with the injector housing. Through direct contact with the injector housing in a circumferential region of the (cylindrically shaped) first component, heat input can be effectively dissipated to the injector housing, thus preventing the second component of the valve seat unit from heating up.

[0051] In further development, a passive valve can also be provided downstream of the valve seat unit, comprising a valve plunger, in particular a sleeve-shaped one, which with its end face facing the valve seat unit is designed to close or release an outlet contour of the through-line, wherein preferably a valve spring is provided which serves to push the valve plunger towards the valve seat unit.

[0052] The primary purpose of this passive valve is to prevent the anchor element, which is lowered onto the valve seat unit, from being forced upwards at very high pressure in a combustion chamber and to avoid possible backfire.

[0053] According to a further advantageous modification of the present invention, it can be provided that the first component of the valve seat unit is circumferentially surrounded by the injector housing in order to provide for a radial dissipation of a heat flow into the injector housing.

[0054] Furthermore, it may be provided that a device for thermal contact with a cooling device for the injector is arranged radially or downstream of the first component of the valve seat unit on the outside of the injector housing, so that the heat flow directed radially into the injector housing can be effectively dissipated.

[0055] Furthermore, according to an advantageous embodiment of the present invention, the layer-like arrangement of the first component may be arranged relative to the second component in the direction of the axial direction of the injector.

[0056] The invention further relates to an internal combustion engine, in particular a hydrogen engine with an injector according to one of the aspects discussed above or a valve seat unit according to one of the aspects discussed above.

[0057] Further features, details, and advantages of the invention will become apparent from the following description of the figures. These show:

[0058] Fig. 1 : a longitudinal sectional view through an injector according to the invention,

[0059] Fig. 2: a representation of different states of components and pressures in an injector,

[0060] Fig. 3: an enlarged section from the sectional view of Fig. 1 focusing on the valve seat unit according to a first embodiment,

[0061] Fig. 4: an enlarged section from the sectional view of Fig. 1 focusing on the valve seat unit according to a second embodiment, Fig. 5: an enlarged section from the sectional view of Fig. 1 focusing on the valve seat unit according to a third embodiment,

[0062] Fig. 6a: a further embodiment of the present invention, in which the valve seat unit has on its side facing the combustion chamber a corresponding shape for interacting with a conically shaped passive valve, and

[0063] Fig. 6b: a detailed view in the transition area between the valve seat unit and the passive valve according to Fig. 6a.

[0064] The following detailed description of the figures in Fig. 1 refers to an injector 1 for injecting hydrogen, but it is clear to those skilled in the art that the invention also includes an injector 1 for injecting gas or another fuel.

[0065] Fig. 1 shows a longitudinal section of the injector 1 according to the invention for injecting hydrogen into a combustion chamber 16. The injector 1 has an injector housing 2 in which various components of the injector 1 are located. A gas connection 11 is provided on the connection side for introducing hydrogen into the injector 1. First, the hydrogen or another combustible fluid is guided through a bore of the gas connection 11, which runs approximately centrally in the injector housing 2, and then through a fluid channel of an armature counterpart 27, a through-opening of the armature 5, and the hollow interior of a valve insert 3 to the end of the valve insert 3 furthest from the connection side 11.

[0066] Depending on the position of the valve insert 3 relative to the valve seat unit 9, the through-lines 4 passing through the valve seat unit 9 are either closed or open. In the state shown in Fig. 1, the through-lines 4 are closed by pressing the valve insert 3 against the valve seat unit 9, since the end face of the valve insert 3 covers the opening contours of the through-lines 4. To improve the seal, sealing elements 30 can be provided that extend around the opening contours of the through-lines 4 and contact the end face of the valve insert 3 when it is in a sealing state. The sealing elements can alternatively or additionally be arranged on the surface of the valve insert 3 facing the valve seat unit.If the through-lines 4 are closed by the front face of the valve insert 3, the fluid flow of hydrogen is stopped at this point of the injector 1 and there is no downstream flow of hydrogen beyond the valve seat unit 9.

[0067] If, however, the openings of the through-lines 4 are released, which is achieved by lifting the valve insert 3 or the anchor element 5 away from the valve seat unit 9, the hydrogen introduced into the injector 1 at a certain pressure flows out of the interior 12 of the valve insert 3 and exits via the multiple through-lines 4 on the side of the valve seat unit 9 spaced away from the valve insert 3. After passing through a check valve 20, 21, which may be provided in the injector 1, the pressurized hydrogen flows through the injection cap 50, which has at least one outlet opening. After passing through this injection cap 50, the hydrogen delivered by the injector 1 is typically located outside the injector 1 in a combustion chamber 16. Air can be added there or through feed openings provided in the injection line.In addition, compression of the hydrogen-air mixture takes place in combustion chamber 16, which then ignites or is ignited.

[0068] The check valve 20, 21, located on the side of the valve seat assembly 9 facing away from the valve insert 3, serves to keep the very high pressure prevailing in the combustion chamber 16 during the expansion phase away from the at least one inlet opening of the valve seat assembly 4. Otherwise, the very high pressure prevailing in the combustion chamber 16 could be transmitted along the passage through the valve seat assembly to the valve insert.

[0069] 3 acts and moves it away from its closing position. In a subsequent step of the injector 1, for example, the hydrogen required for combustion would no longer be introduced into the combustion chamber 16, but rather a mixture that is already at least partially combusted, which can lead to an interruption of the combustion process or, at best, to a reduced combustion efficiency.

[0070] The check valve 20, 21 has a valve tappet 20 and a valve spring 21, which forces the valve tappet 20 in a closing direction, so that hydrogen only flows out through the outlet contour of the valve seat assembly 9 if the through-line 4 running through the valve seat assembly 9 carries a gas at a pressure high enough to overcome the force of the valve spring 21 that forces the valve tappet 20 in the closing direction. This prevents fluid from flowing in from the side of the check valve 20, 21 facing the combustion chamber 16 towards the armature element 5.

[0071] The optionally hollow valve insert 3, together with the other components of the armature element 5, is movable back and forth in the longitudinal direction of the injector 1. The movement of the valve insert 3 is controlled by a solenoid valve. The valve insert 3 is rigidly connected to an armature 5, which in turn reacts to the magnetic force generated by a coil 13. The coil 13 can optionally be energized such that the resulting magnetic force moves the armature 5 towards the gas connection 11. This movement also moves the valve insert 3, which is rigidly connected to the armature 5, causing the valve insert 3 to rise relative to the valve seat unit 9. This raises the flow lines.

[0072] 4 in the valve seat assembly 9 is released, allowing hydrogen (or another fuel) to flow through the valve seat assembly 9. Possible methods for attaching the valve insert 3 to the armature 5 include, for example, crimping, a screw connection into the armature 5, bonding, or other suitable fastening options. To improve the magnetic flux of the solenoid valve, the coil 13 can be surrounded on its outer surface by an iron backplate 25, in which the magnetic field can propagate particularly well. The same applies to the housing component directly surrounding the armature 5 and the armature counterpart 27, which is also preferably made of a magnetizable material. Thus, it can be advantageous if the pole tube, which is a component of the injector housing 2, is also made of iron or another ferromagnetic material.The same applies to the armature counterpart 27, which is advantageously also made of a magnetizable material.

[0073] Fig. 2 shows the basic behavior of injector 1 during injection. In the initial position at time t0 at bottom dead center (BDC) of a cylinder piston interacting with the injector, valve insert 3 and valve tappet 20 are moved into their respective closing positions by the pre-tensioned valve insert 3 and the valve spring 21, respectively, to close the throttle ports A1 and A2, which connect the actuator chamber to the valve chamber and the valve chamber to the injection chamber when valve insert 3 and valve tappet 20 are open. The pressure in injector 1 corresponds to the pressure in the supply line, while the pressure in combustion chamber 16 and in the injection chamber corresponds to the boost pressure during the intake phase of the cylinder piston, in which fresh air is drawn into combustion chamber 16 via the intake valves. The pressure in the valve chamber is approximately equal to the combustion chamber pressure and depends, among other things, on the pressure in the cylinder.The pressure depends on the valve spring 21, the pressure in the combustion chamber 16 during the phase of expelling the hot combustion gases via the exhaust valves of the combustion chamber 16, and any preceding injections. The functional description below is simplified and does not consider the charge exchange caused by the opening and closing of the intake and exhaust valves of the combustion chamber 16.

[0074] At time t, a control unit applies a voltage signal via the electrical contacts to the coil 13 of the actuator, causing the current F1 in the electrical circuit to rise to a defined final level. The current-carrying coil 13 induces a magnetic field in the actuator, whose magnetic field lines 24 spread out in a torus shape around the coil 13 (see Fig. 1). This magnetic field generates a magnetic force F2 in the air gap 15 between the armature 5 and the armature counterpart 27, causing the armature 5 to be attracted to the armature counterpart 27 at time t2 as soon as the magnetic force F2 exceeds the closing force (sum of the preload force of the armature spring 17 and the pressure forces on the valve insert 3 and the armature 5). The build-up of the magnetic field, and thus of the magnetic force F2, is delayed by eddy currents in the iron components of the magnetic circuit.The armature 5 is fixedly connected to the valve insert 3 or forms a one-piece armature-valve insert assembly, such that the valve insert 3 moves uniformly with the armature 5 along a stroke F3. As soon as the previously compressed, elastic sealing element 30 (e.g., arranged on the valve insert 9) is no longer in contact with the end face of the valve insert 3 at time t3, the connection between the actuator chamber and the valve chamber is released, allowing fuel to flow from the actuator chamber into the valve chamber. This increases the pressure in the valve chamber. As soon as the pressure difference between the valve chamber and the injection chamber corresponds to a force difference on the valve tappet 20 equal to the preload force of the valve spring 21, the passive valve opens; that is, the valve tappet 20 moves away from the seat along a valve tappet stroke F4 and releases the connection between the valve chamber and the injection chamber, allowing fuel to flow from the valve chamber into the injection chamber.This results in a pressure increase in the injection chamber (see F8 Pressure in the injection chamber). The fuel flows downstream through the opening in the injection line 50 into the combustion chamber 16. The injection line 50 is advantageously designed such that the flow can be introduced into the combustion chamber 16 in a defined state (jet orientation, inlet pulse, jet pattern, etc.). The lifted state of the valve insert 3 and valve tappet 20 is maintained throughout the entire remaining injection phase. The flow level can be reduced (e.g., by a PWM voltage signal) as soon as the valve insert is fully open and any potential rebound does not lead to the valve insert 3 closing. During injection, the engine cylinder is in the compression phase, so the combustion chamber pressure F5 increases steadily.To terminate the injection process, the control unit cuts off the power supply, reducing the current F1 through coil 13 to zero (time t4). Due to the eddy currents, the magnetic force F2 also decreases with a time delay. As soon as the magnetic force F2 is less than the sum of the closing force of the armature spring 17 and the hydraulic forces on the valve insert 3 and the armature 5, the valve insert 3 and armature 5 begin to close uniformly (time t5); see also F3, F4. When the end face of the valve insert 3 contacts the sealing element 30 of the valve seat unit 9 (which can also be located on the valve insert 3), the connection between the actuator chamber and the valve chamber is severed, and the fuel flow from the actuator chamber to the valve chamber is interrupted (time t6). This causes the pressure in the valve chamber F7 to drop.When the pressure difference between valve chamber F7 and injection chamber F8 corresponds to a force difference on the valve tappet 20 equal to the valve spring force and other forces acting in the closing direction, the valve tappet 20 moves back to its closed position on the valve seat 21 and is pressed against the seat 21 by the increasing pressure F5 in the combustion chamber 16 and thus in the injection chamber, so that the fuel connection between the valve chamber and the injection chamber is interrupted (possibly after a period of tappet bounce against the valve seat 21) (time points t6-t7). The injection process is thus completed.During the further compression phase of combustion chamber 16 up to top dead center (TDC) in the period t7-t8, the air-fuel mixture in the injection chamber is compressed, while in the subsequent expansion phase it expands (period t8-t9). For the sake of simplicity, the further interim increase in combustion chamber pressure F5 due to combustion is not shown here. If the pressure in combustion chamber 16 drops so low that the difference in pressure forces on the valve tappet 20 corresponds to the preload force of the valve spring 21 (time t9), the valve tappet 20 opens briefly again, allowing some of the fuel present in the valve chamber to escape into combustion chamber 16. This process depends on the spring force and can occur repeatedly (period t9-t1). 10 ). The respective mass flow of the fuel via the injection openings 4, the opening contour 19 and the at least one outlet opening 51 is indicated by F9, F10 and F11 respectively.

[0075] Fig. 3 is an enlargement of the sectional view in Fig. 1 and shows an embodiment of the present invention in which the valve seat unit 9 comprises a first component 31 and a second component 32. The two components 31 and 32 are thermally separated from each other by an insulating component 33, so that the thermal conductivity between the first component 31 and the second component 32 is relatively low through the insulating component 33. When a combustion process occurs in the combustion chamber 16, this also leads to an increase in the temperature of the first component 31, but due to the arrangement of the insulating component 33, this no longer directly leads to an increase in the temperature of the second component 32.

[0076] By laterally enclosing the first component 31 with the injector housing 2, the heat flow is directed radially into the injector housing 2, from where it can then be dissipated via an external cooling device, for example, a water sleeve. The heat flow shown by the arrows in Fig. 3 therefore does not run axially towards the second component 32, so that excessive heating of a sealing element 30 for sealing the opening contour of the second component of the valve seat unit 9 cannot occur.

[0077] By providing, according to the invention, a very low thermal conductivity between the first component 31 and the second component 32 of the valve seat unit 9, the heat flow no longer runs axially from the first component 31 to the second component 32, but initially radially into the injector housing 2 enclosing the first component 31. Since the injector housing 2 typically has a cooling device, which can be arranged at the level of the first component 31 or downstream at the level of the check valve 20, 21, the heat flow directed radially outwards into the injector housing is efficiently dissipated and prevented from propagating into the second component 32, thus preventing excessive heating of a sealing element 30 or the like. The service life and functionality of the sealing element 30 can thereby be improved or extended.

[0078] Furthermore, it can be seen that the through-lines 4 have an opening contour in the form of a circumferential groove 34 at their end facing the anchor 5.

[0079] Due to its design as a circumferential groove 34 in the surface of the second component 32 facing the anchor, the sealing element 20, which is generally ring-shaped, has a smaller contact area with the second component 32, so that only a small proportion of heat can be transferred from the valve seat unit 9 to the sealing element 20. This also contributes to reducing the temperature of the sealing element 30.

[0080] Furthermore, the circumferential groove 34 on the side of the valve insert 32 facing the sealing element 30 also leads to an improvement in the inflow behavior, especially with small strokes of the valve insert 3.

[0081] In addition, a circumferential groove can also be provided on the end face of the second component 32 facing the first component 31, so that regardless of a rotational orientation of the two components, a flow in the same direction is always generated through the valve seat unit 9.

[0082] The first component 31 can thus be designed to have a plate-like base body in which both flat sides are connected by at least one passage penetrating the base body. This passage can be, for example, a bore or the like. The groove surrounding the first component ensures optimal coverage of the free flow cross-sections, regardless of the rotational orientation. Furthermore, the minimum cross-sectional area of ​​the flow path (which can also be implemented by multiple paths) can be arranged along the flow path 4 running through the valve seat unit 9 in the first component 9. This is advantageous because the minimum cross-sectional area controlling the injection quantity is then located in a component that is relatively simple and can be modified with minimal effort.

[0083] The insulation component 33 can, for example, be designed in a ring-like form, but the invention also includes the placement of individual insulation component pins in the first component 31 and / or in the second component 32.

[0084] It can further be seen that the second component 32 is stacked on top of the first component 31, with the stacking direction extending in the axial direction of the injector 1. The first component 31 is axially spaced from the second component 32. In Fig. 3, the insulating component 33 provides this space.

[0085] Fig. 4 is a modification of the sectional view from Fig. 3, wherein the valve seat assembly 9 is designed according to a further embodiment. Whereas in the previously discussed Fig. 3 the valve seat assembly was depicted by stacking the first component 31 opposite the second component 32 and the insulating component 33 arranged between them, the first component 31 is now welded to the second component 32. The weld seam 35 is provided on a radially outward-extending edge or edge section and does not necessarily have to extend over the entire circumferential side of the valve seat assembly 9. Furthermore, care must be taken to ensure that the weld seam 35 is thin-walled so that the thermal conductivity between the first component 31 and the second component 32 is not excessive and the advantages of the invention can still be achieved.An advantage of this embodiment is that the first component 31 and the second component 32 now form a valve seat unit 9 that is firmly connected to each other, and whose assembly in the injector 1 is faster.

[0086] Fig. 5 is a modification of the sectional view from the preceding Fig. 4, showing the valve seat assembly 9 according to a third embodiment. This is based on the embodiment of the previously discussed Fig. 4, wherein an additional insulating component 33 is now provided in the dead space formed by the spacing of the first component 31 from the second component 32. The primary function of this insulating component is to reduce the volume of the dead space in order to minimize the amount of fuel inserted into the valve seat assembly and to provide mechanical support.

[0087] Fig. 6a shows a further embodiment of the valve seat unit 3, wherein the first component 31, which faces the combustion chamber 16, interacts with a passive valve whose valve tappet 20 has a conical shape in its region facing the valve seat unit 3. The through-line 4 of the valve seat unit 3 is thus blocked or opened by the valve tappet 20 depending on the prevailing pressure conditions, with the through-line being arranged centrally in the illustrated embodiment. The seating surface between the valve tappet 20 and the first component 31 of the valve seat unit 3 is minimized due to the coordinated conical shape, thus also reducing thermal heat transfer between these components.Furthermore, it is possible to ensure low-loss fuel transport along these bores 23 by means of inclined bores 23, which lead from an outside of the valve tappet 20 to an inside of the valve tappet.

[0088] For example, several such equidistant bores, e.g., 2, 4, or 6, may be provided to direct the fuel flowing towards the combustion chamber 16 when the through-line 4 is not closed. The conical design of the passive valve with an exemplary seat angle in the range of 100–140°, preferably 110–130°, and particularly 115–125°, represents an implementation that is advantageous both with regard to good space filling (in this case, the combustion chamber 16) and with regard to high wear resistance.

[0089] Furthermore, the combination of the seat angle and the diagonally arranged transverse bores, which run from an outside of the valve tappet to an inside, leads to very high possible mean pressures in the combustion chamber.

[0090] Fig. 6b shows the seat angle a and the angle β of the transverse bores 23. In the illustrated embodiment, the seat angle a is 120° and the angle β of the transverse bores is 60°.

[0091] Reference symbol list:

[0092] 1 injector

[0093] 2 injector housings

[0094] 3 valve insert

[0095] 4 through lines

[0096] 5 anchors

[0097] 9 Valve seat unit

[0098] 11 Gas connection

[0099] 12 Bypass

[0100] 13 coil

[0101] 14 Interface for cooling

[0102] 15 air gap

[0103] 16 Combustion chamber

[0104] 17 Anchor spring

[0105] 19 Passive valve

[0106] 20 Valve tappets of the check valve

[0107] 21 Valve spring of the check valve

[0108] 22 Seat surface of the check valve

[0109] 23 slanted transverse bores in the check valve

[0110] 24 magnetic field line

[0111] 25 Iron conclusion

[0112] 27 Anchor counterpart

[0113] 30 sealing element

[0114] 31 first component

[0115] 32 second component

[0116] 33 Insulation component

[0117] 34 circumferential grooves

[0118] 35 weld seam

[0119] 36 slots / bores with minimum conductor cross-section

[0120] 50 blowing line

Claims

Claims 1. Valve seat unit for an injector for injecting fuel, preferably for injecting a gaseous fuel, in particular hydrogen, comprising: at least one through-line extending through the valve seat unit for conveying fuel, wherein an opening contour of the at least one through-line is designed to interact with an anchor element in order to close or open the through-line for fuel flow by placing or lifting the anchor element from the valve unit, characterized in that the valve seat unit comprises at least a first component and a second component, which are arranged one above the other, in particular in a layered manner, wherein the first component and the second component are thermally separated from each other in such a way that the thermal conductivity from the first component to the second component is no more than 0.3 W / (m K), preferably no more than 0.1 W / (m K) and preferably not more than 0.05 W / (m K).

2. Valve seat assembly according to the preceding claim 1, wherein the first component and the second component are arranged spaced apart from each other. and preferably connected to each other by a welded joint, wherein preferably the welded joint is formed either at a point or continuously and / or represents the only direct connection between the first component and the second component.

3. Valve seat assembly according to one of the preceding claims, wherein an insulating component is arranged between the first component and the second component, which prevents direct contact between the first component and the second component and / or reduces a dead space formed by the spacing of the first component from the second component, wherein the insulating component preferably has a low thermal conductivity not exceeding 0.3 W / (m K), preferably 0.1 W / (m K), and / or is made of a ceramic material.

4. Valve seat unit according to one of the preceding claims, wherein the first component and the second component of the valve seat unit do not directly contact each other, preferably wherein the first component and the second component are connected to each other via an insulating component and / or a welded connection.

5. Valve seat unit according to one of the preceding claims, wherein the first component comprises an outlet contour of the at least one through-line and the second component comprises the opening contour of the at least one through-line.

6. Valve seat assembly according to one of the preceding claims, wherein the first component and / or the second component has a thermal conductivity greater than the thermal conductivity between the first component and the second component, preferably wherein the thermal conductivity of the first component and / or the second component is at least 1 W / (m K), preferably at least 10 W / (m K).

7. Valve seat unit according to one of the preceding claims, wherein the second component has a first flat side in which the opening contour of the through-line is arranged, wherein the opening contour is a circumferential groove formed in the first flat side, preferably wherein at least one line section, in particular in the form of a bore or a slot, extends from a groove base of the circumferential groove to a transfer contour of the through-line for directing a fuel to the first component of the valve unit.

8. Valve seat unit according to one of the preceding claims, wherein the second component has a second flat side facing the first component and in which a transfer contour of the through-line for directing a fuel to the first component is arranged, wherein the transfer contour is a circumferential groove formed in the second flat side, preferably wherein at least one line section, in particular in the form of a bore or a slot, is formed from a groove base of the circumferential groove towards the opening contour of the valve unit.

9. Valve seat unit according to one of the preceding claims, wherein the first component has a plate-like base structure with a first flat side and a second flat side, wherein the first flat side faces the second component and the second flat side faces away from the second component and has an outlet contour of the valve unit, preferably wherein a through-line section connecting the first flat side and the second flat side of the first component defines a minimum line cross-section along the through-line of the valve unit.

10. Valve seat assembly according to one of the preceding claims, wherein the first component and / or the second component is / are rotationally symmetrical.

11. Injector (1 ) for injecting fuel, preferably for injecting a gaseous fuel, in particular hydrogen, comprising: an injector housing for receiving and arranging injector components, an anchor element which is movably arranged in the injector housing along an axial direction of the injector, and a valve seat unit according to one of the preceding claims, wherein the anchor element is designed to close or release the through-line of the valve seat unit by means of an axial movement in order to enable or prevent fuel flow through the through-line.

12. Injector according to the preceding claim 11, wherein a passive valve is further provided downstream of the valve seat unit, comprising a valve plunger, in particular a sleeve-shaped one, the end face of which is designed to close or release an outlet contour of the through-line with respect to the valve seat unit, wherein preferably a valve spring is provided which serves to push the valve plunger towards the valve seat unit.

13. Injector according to the preceding claim 12, wherein the valve plunger of the passive valve comprises a conical section or is conically shaped on its end face facing the valve seat assembly and interacts with a correspondingly inversely shaped contour of the first element of the valve seat assembly to block or release the flow line.

14. Injector according to the preceding claim 13, wherein the conical section or conical shape of the valve tappet, together with the corresponding seat surface of the first element of the valve seat assembly, has a seat angle (a) in the range of 100-140°, preferably 110-130° and preferably 15-125°, and / or the valve tappet is sleeve-shaped and has at least one transverse bore having an outer surface and an inner surface of the valve tappet. connects, wherein the transverse bore encloses the angle of the longitudinal direction of the valve tappet, which lies in a range of 30-70°, preferably 40-60° and preferably 45-55°.

15. Injector according to one of the preceding claims 11 or 14, wherein the first The component of the valve seat assembly is circumferentially surrounded by the injector housing to provide radial dissipation of heat flow into the injector housing.

16. Injector according to any one of the preceding claims 11 to 15, wherein the layered arrangement of the first component is arranged relative to the second component in the direction of the axial direction of the injector.

17. Internal combustion engine, in particular a hydrogen engine with an injector according to one of the preceding claims 11 to 16 or a valve seat assembly according to one of the preceding claims 1 to 10.

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